Nonequilibrium argon plasma flows in a circular tube were generated by an electrodeless discharge at the conditions of low input powers (30-70W)and low pressures (0.27-1.33kPa). Electron current was collected by an unsymmetric double probe and analysed to obtain electron temperature and electron density by taking account of non-MAXWELL electron energy distribution and the reflection of electrons on probe surface. Radiative properties of the plasmas were measured spectroscopically to examine electronic excitation nonequilibrium and the effect of non-MAXWELL electrons. The generated plasmas were found to have electron temperature of 3-4×104K and electron density of -1011 cm-3 and to be extremely in thermo-chemical nonequilibrium. It is emphasized that the consideration of non-MAXWELL electrons is important in the interpretation of the characteristic of collected electron current and the radiative properties of plasmas.
Pitch damping of ducted rotor is important to study dynamic stability of ducted rotor type VTOL aircraft. In this paper, pitch damping of a ducted rotor has been studied by using unducted and ducted model rotors in rocking motion. These rotors have semi-rigid blades with spring constrained hinges. The spring is made of FRP plate and by different combination of the plates as the hinge stiffness of blade can be changed. At first the relation between pitch damping and hinge stiffness of unducted rotor has been studied experimentally. The result has coincided those with AzuMA and NAKAMVRA's paper.5) Nextly, the theoretical analysis has been conducted about pitch damping of the ducted rotor based on momentum theory and the result has been examined experimentally. As the result of the analysis, it is pointed out that the pitch damping of ducted rotor consists of three parts, viz., increased pitch damping of rotor owing to the decrease of blade tip loss, pitch damping by momentum change of duct inflow in rocking motion and negative pitch damping (divergent force) by duct lip. It has been clearly shown in the experimental result that the pitch damping of the ducted rotor is stronger than that of unducted rotor.